A Blue View: The Fierce Feeding Tactics of Nudibranchs

Published March 17, 2015

The brilliantly colored creatures owe it all to their food. Epitomizing the expression “You are what you eat,” nudibranchs derive their vibrant hues from their prey, which ranges from algae, sponges and anemones to barnacles, corals and even other nudibranchs.

As you probably guessed, sea slugs aren’t the quickest predators, and their tiny eyes provide limited sight. But nudibranchs are hardly helpless. On their heads, two highly sensitive tentacles, called rhinophores, allow them to smell, taste and feel their way around. These appendages receive chemical signals helping them to identify potential prey.

Once they’ve found their next meal, nudibranchs scrape up their food with a file-like organ on the mouth, called a radula. It’s covered with chitinous teeth that help tear apart their prey. Pretty fierce for a delicate-looking sea slug, right?

Nudibranchs aren’t afraid to be adventurous with their food either, chowing down on the poisonous anemones that most aquatic creatures avoid. The sea slugs sneak up on their poisonous prey; raise themselves above the anemone, carefully dodging tentacles; and then invert their mouths and dive into their dinner.

Once the anemone realizes what’s happening and withdraws its tentacles, it’s usually too late. The digestion process has already begun. What’s more, the sea slug is simultaneously stealing the anemone’s defense mechanism, storing the stinging tentacles underneath its own skin. Predators beware: This nudibranch is now armed and dangerous.

To learn more about nudibranchs, listen to this week’s A Blue View podcast!